5.2.3 Electrode Potentials and Fuel Cells

Question 1

explain, for simple redox reactions, the terms

redox, oxidation number, half-reaction,

oxidising agent and reducing agent

Question 2

construct redox equations using relevant half equations

or oxidation numbers;

Question 3

interpret and make predictions for reactions

involving electron transfer.

Question 4

define the term standard electrode (redox)

potential, E o ;

Question 5

describe how to measure, using a hydrogen electrode, standard electrode potentials of:

(i) metals or non-metals in contact with

their ions in aqueous solution,

(ii) ions of the same element in different

oxidation states;

Question 6

calculate a standard cell potential by

combining two standard electrode potentials;

Question 7

predict, using standard cell potentials, the

feasibility of a reaction;

Question 8

consider the limitations of predictions made

using standard cell potentials, in terms of

kinetics and concentration;

Question 9

apply principles of electrode potentials to

modern storage cells;

Question 10

explain that a fuel cell uses the energy from

the reaction of a fuel with oxygen to create a

voltage;

Question 11

explain the changes that take place at each

electrode in a hydrogen–oxygen fuel cell

Question 12

outline that scientists in the car industry are

developing fuel cell vehicles (FCVs), fuelled

by:

(i) hydrogen gas,
(ii) hydrogen-rich fuels;

Question 13

state advantages of FCVs over conventional

petrol or diesel-powered vehicles, in terms of:

(i) less pollution and less CO2,
(ii) greater efficiency;

Question 14

understand how hydrogen might be stored in

FCVs:

(i) as a liquid under pressure,
(ii) adsorbed on the surface of a solid

material,

(iii) absorbed within a solid material;

Question 15

consider limitations of hydrogen fuel cells, for

example:

(i) storing and transporting hydrogen, in terms of safety, feasibility of a pressurised liquid and a limited life cycle of a solid ‘adsorber’ or ‘absorber’,
(ii) limited lifetime (requiring regular replacement and disposal) and highproduction costs,
(iii) use of toxic chemicals in their production (see also unit F322: 2.4.2);

Question 16

comment that a ‘hydrogen economy’ may contribute largely to future energy needs but

limitations include:

(i) public and political acceptance of hydrogen as a fuel,
(ii) handling and maintenance of hydrogen systems,
(iii) initial manufacture of hydrogen,

requiring energy.